Introduced by a party official as a modern-day Julius Caesar, the 57-year-old former paratrooper was greeted by chants of "Generale, Generale, Generale" as he took to the stage of Futuro Nazionale's inaugural congress.
"We represent the rejects and the dregs, and are proud of it," said Vannacci, who is looking to outflank Meloni's conservative coalition on the right, four months after quitting Deputy Prime Minister Matteo Salvini's League party.
Vannacci's populist movement is already polling at close to five per cent, closing in on the League and potentially clouding Meloni's hopes of regaining power in next year's national vote, unless she forges an electoral pact with him.
However, such a tie-up would carry major risks for Meloni and potentially scare away moderate supporters deterred by Vannacci's anti-EU, pro-Russia agenda and his close ties to far-right European parties such as Germany's AfD.
Positioning himself as the most hawkish voice on immigration in Italy, Vannacci said on Sunday he would slash the number of foreigners living in Italy to some four per cent of the total population from an estimated 12 per cent at present.
"We don't have a program for immigration, we have a program for re-migration," he said to cheers.
Unveiling its program at the weekend, Futuro Nazionale embraced many of the policies that Meloni had championed during her years in opposition, before she took charge of Italy's debt mountain in 2022 and had to reassure investors.
Vannacci said he wanted a discussion on Italy's membership of the euro single currency.
He also proposed abandoning the EU's Green Deal, aimed at drastically cutting carbon emissions, and ending Italy's ban on nuclear power.
The program also backed incentives for families, including tax cuts for those with children.
Though Italy has one of the lowest rates for murder and violent crime in the world, Vannacci said his first priority would be security and defence, vowing zero tolerance for criminals and promising to build more prisons.
Vannacci has accused Meloni of reneging on many of her campaign pledges, but he acknowledged that his own program was not set in stone.
"No plan survives the first shot in battle ... it has to be adapted to reality," he said.
